A shoe, especially an athletic shoe, is generally composed of an outsole which makes direct contact with the ground surface, a midsole of elastic material and arranged on the outsole, a shoe upper of an appropriate height and extending upwards from the periphery of the midsole, and an insole disposed on the midsole and surrounded by the shoe upper. The insole and the shoe upper form together a space to accommodate a human foot. The insole and the midsole serve to enhance the wearing comfort of the shoe.
The athletic shoe described above is generally defective in design in that the shoe is poorly ventilated that the heat and the perspiration of the foot wearing the shoe are bound to remain in the space surrounded by the shoe upper, thereby producing the foul air inside the shoe.
With a view to improving the ventilation of the shoe, the shoe upper is provided with some breathing holes in communication with the inside of the shoe. However, such breathing holes are not effective in letting out the foul air for the reasons which are expounded hereinafter.
The ventilating effect of the breathing holes is often undermined by the fact that the foot wearing the shoe obstructs the passage of the foul air as well as the fresh air.
The foot and the shoe upper covering the foot form a sealed space which is incapable of letting out the foul air and of letting in the fresh air.
In order to overcome the shortcomings of the conventional shoe described above, some of the shoe makers have introduced a new kind of shoe midsole which is provided therein with a compressible hollow interior capable of driving out the foul air, as exemplified in the Taiwanese Patent Number 134162. However, the cost of making the compressible midsole of the prior art is prohibitively high in view of the fact that the compressible hollow interior of the midsole must be formed by the method of hollow die casting. In addition, the air ducts so formed are often obstructed easily, thereby undermining the airing effect of the prior art midsole. As a result, such prior art midsole has never been accepted enthusiastically by the shoe makers at large.